1. Field of the Invention
This invention relates to hot air heat exchanger furnaces, and more particularly to a hot air heat exchanger furnace that use biomass (crop residue) as a fuel source.
2. Background
It has been found that use of biomass (crop residue) as a source of fuel for various heating demands is highly desirable because of its renewability, accessibility, low cost, and its substantial BTU content. For example, in many grain farming operations involving the raising of corn and the like, it has been the common practice during harvesting to allow the crop residue such as stalks and associated parts thereof, as well as the cobs where shelling of the corn occurs in the field, to remain in the field to assist in controlling soil erosion and to effect partial replenishment of various soil nutrients and organic content for subsequent plantings. However, all such residue is not required for these purposes. In some instances, e.g., where the residue is accumulated at a processing point, such as peanut shells at a shelling plant, disposal of the residue is a problem. Moreover, in some areas, crop residue is burned in the field for disposal. Because of the substantial costs of conventional fuels (i.e., oil, natural gas, propane, etc.), it has been found that such crop residue could be utilized as a fuel for producing the heat required for various purposes, such as the drying of grains, peanuts, soybeans and other materials and for the heating of buildings. The furnace illustrated and described herein is useful in such applications.
It is desirable that hot air heat exchanger furnaces have characteristics that increase operating efficiency and reduce heat loss. These characteristics include: a combustion chamber with a large radiating surface; long exhaust tubes placed within the furnace to constrain the combustion gases and pass them over the large radiating surface of these tubes; and an arrangement of components that restricts the movement of the air through the furnace, allowing it to come into close association with the heat radiating surfaces. It is also desirable that these furnaces be of a simple, rugged and inexpensive design. The furnace illustrated and described herein has all of these characteristics.